# How to place circles that there will be no gap. Use least number of circles possible.

by Firewolffzc
Tags: circle
 P: 7 I have to plan the layout of a sprinkler system. Basically, each sprinkler shoots a radius of 7.5 feet water, and I want every part of the floor covered with water. How can I use the least number of sprinklers?
 Sci Advisor HW Helper Thanks P: 26,148 Hi Firewolffzc! Welcome to PF! Tell us what you think, and then we'll comment!
 P: 7 Well, I think I figured one way to approach. Is it better to imagine not the circle, but a triangle, square or hexagon inscribed within the circle, because these shapes can link without gaps. Then once done with these shapes, I draw a circle circumscribing the shape. I was wondering if this was an effective method. If it is, which shape is best?
 Sci Advisor HW Helper Thanks P: 26,148 How to place circles that there will be no gap. Use least number of circles possible. yup, that seems a good idea! i'd guess it's the hexagon, but you'd better do the maths!
 P: 7 Well, see, I don't know what math to do! I figured out that the reason we can use triangles, squares and hexagons is because the measurement of their angles are multiples of 360. (triangle)60*6=360, (square)90*4=360, (hexagon)120*3= 360. Well, it is not possible to have a shape with a 180 or 360 degrees angle, therefore hexagons are the best shape because they make the smallest area between circles. Wow, I can't believe I figured that out myself. Anyway, is there more to it or is this the final solution?